Technical Field
The present disclosure relates to a radar apparatus.
Background Art
Conventionally, as an example of a radar apparatus, a dual-frequency CW (continuous wave) radar apparatus is known. In the dual-frequency CW radar apparatus, two radar waves having different frequencies are emitted. Then, based on the received signals of the reflected waves, the distance to the target that has reflected the radar waves, and the speed and the azimuth of the target are detected.
Patent Literature 1 JP-A-2010-060459
According to this radar apparatus, when a plurality of targets having the same speed are present in the forward direction, the Doppler frequencies of the reflected waves that are generated by these targets may coincide with one another. This leads to the appearance of synthetic components of the reflected waves from the plurality of targets in the received signals (multipath interference conditions). Under these conditions, distances or azimuths are erroneously detected.
In light of such a problem, JP-A-2010-060459 proposes performing judgement for a plurality of times as to whether or not the signal intensity is different between receiver antennas. According to the proposal, if no judgement is made that the signal intensities are different, it is judged that multipath interference is not present. Otherwise, it is judged that multipath interference is present.
In spite of the presence of synthetic components, the signal intensity between the receiver antennas could happen to be the same. According to PTL 1, the judgement as to whether the signal intensity is different is ensured to be performed for a plurality of times at intervals to enhance the accuracy of judgement on the multipath interference conditions.
Synthetic components are generated in received signals only during a very short time. Therefore, according to the patent literature mentioned above, the judgement performed a plurality of times has a limitation in enhancing the accuracy of judgement on the multipath interference conditions. Further, since a judgement has to be made a plurality of times, it takes time before the multipath interference conditions are detected.